Updraft carburetor body and method for making the same



A g- 8. 9 M. F. STERNER UPDRAFT CARBURETOR'BODY AND METHOD FOR MAKING THE SAME Filed April 7, 1965 2 Sheets-Sheet l m/uz-wroe Ma W F. STER/VER U) ATTORNEY Aug. 8, 1967 M. F. STERNE'R UPDRAFT CARBURETOR BODY AND METHOD FOR MAKING THE SAME Filed April 7, 1965 2 Sheets-Sheet 2 AZTORA/E'Y MEZ VIN F. 5 TERA/6R United States Patent 3,334,878 UPDRAFT CARBURETOR BODY AND METHOD FOR MAKING THE SAME Melvin F. Sterner, Bloomfield Hills, Mich., assignor to Holley Carburetor Company, Warren, Mich., a corporation of Michigan Filed Apr. 7, 1965, Ser. No. 446,344 4 Claims. (Cl. 261-72) This invention relates to internal combustion engine carburetors, and more particularly to a single piece body, and method of making the same, for updraft type carburetors for engines driving agricultural type tractors.

Io applicants knowledge, it has been and is the universal practice to employ updraft type carburetors having a generally L-shaped induction pass-age for agricultural and industrial type tractor engines, and there are good reasons for this. One reason for avoiding a downdraft type carburetor is that it is mounted at the top of the engine, which would necessarily raise the hood level and interfere with the operators visibility. A reason for avoiding horizontal carburetors is that side clearance must be maintained; that is, tractors are often provided with power equipment which may include movable hydraulic cylinder-s mounted to the tractor frame close to the side of the engine. Also, tractors of this type often operate under adverse conditions, such as in wooded terrain where tree branches and other similar obstacles may damage a horizontal draft carburetor or other part extending laterally from the engine.

Another problem is that almost all tractors of this kind have fuel tanks mounted above or high at one end of the engine, providing a gravity fee-d and eliminating the need of a fuel pump. If a downdraft carburetor were employed and the fuel inlet valve stuck open, the entire contents of the fuel tank would drain directly into the engine, causing dilution of the crank case oil and hydraulic locking of the engine cylinders. With an updraft carburetor, the fuel will merely spill onto the ground.

Another feature of' prior art tractor carburetors is that the bodies thereof are, almost without exception, made from cast iron sand castings. In the tractor industry, the tradition has been durability and ruggedness; cast iron supplies those properties, and there has been a natural reluctance to change to other modern materials such as aluminum.

Almost all prior art tractor carburetors are cast in two sections, a throttle body section and a fuel bowl and air horn section which are subsequently assembled with a gasket therebetween, the gasket always being a potential point of leakage. The fuel metering body is, in all cases, formed integrally with the fuel bowl; that is, one side of the metering body is attached to the inner wall of the fuel bowl so that it is not subjected on all sides thereof to the cooling effect of the fuel in the bowl. The latter construction, together with the fact that tractors of this kind have an open engine compartment and are operated for long periods of time, often under direct exposure to the heat of the sun, so that the engine fan provides less efiicient cooling than the fan in a passenger car having -a closed engine compartment, causes heat problems resulting in metering of fuel vapors along with solid fuel for which the carburetor was calibrated. This heat problem is further aggravated by the fact that cast iron has a lower specific heat and lower heat conductivity, as compared to other materials such as aluminum.

Of necessity, the capacities of prior art cast'iron tractor carburetors are varied by machining or a press -fit venturi; in the latter case, a different venturi is inserted into the induction passage of the same carburetor body when it is desired to change the capacity of the carburetor. Furthermore, sand coring of cast iron provides rough passage surfaces which have to be machined or enlarged to maintain efficiency or flow capacity; also, it does not permit coring the many small passages required in a carburetor so that costly machining is required. In any event, cast iron cannot be die cast because its high melting point would soon damage the dies.

As opposed to sand casting, die casting provides smooth surfaces which often need not be machined. It also provides closer tolerances, enables thin sections, which are desirable in aluminum castings to avoid porosity, and gives a weight to strength ratio comparable to cast iron. While the permanent dies required for die casting process are very costly and cannot be justified except for relatively high volume production, tractor carburetor volumes appear to be increasing so that the tooling appears justified; also, die casting materials, such as aluminum, for carburetor bodies has now been accepted in the passenger vehicle field.

A recent development in the agricultural tractor field is a three cylinder engine having relatively severe pulsations in the intake manifold. By close observation, it was discovered that running this engine at Wide open throttle with certain prior art tractor carburetors and without an air cleaner causes a considerable amount of fuel to be ejected from the carburetor air inlet.

This problem does not occur when running the same engine under the same conditions with a carburetor having a body formed in a manner proposed herein, It is believed that this is attributable to the fact that a carburetor body made according to the invention provides a reservoir in the air inlet directly below the venturi that apparently absorbs or dampens the engine pulsations. That is, the opening at the bottom of the carburetor body required to withdraw the core is closed by a flat plate against which the pulsations impinge and bounce back toward the ventur-i, tending to oppose the next pulsation and improving engine operation. 7

At least some portion of the fuel ejected from the air inlet of prior art carburetors due to severe pulsations would be at least temporarily lost in the air cleaner, resulting in faulty distribution of the fuel. However, with a carburetor made according to the invention, pulsations are reduced and the fuel is not ejected from the air inlet; therefore, the fuel distribution is improved. This has been observed by running a carburetor made according to the invention with a flat Plexiglas plug to close the core opening at the bottom of the carburetor; specifically, it has been observed that engine pulsations cause fuel to be alternately deposited and immediately removed from the Plexiglas plug. This immediate recapture of a lesser amount of pulsated fuel obviously results in improved engine operation. In other words, any pulsated fuel has sufiicient inertia so that it deposits on the flat closure for the core opening, rather than entering the air inlet, as it does in prior art carburetors wherein the junction of the air inlet and the bore is formed with a radius or the junction contains structure having surfaces from which the fuel can deflect into the air inlet.

Accordingly, an object of the invention is to provide an updraft carburetor body that can be die cast so as to reduce carburetor machining and assembly costs.

Another object of the invention is to provide, for use on tractor and other similar engine applications, a onepiece updraft carburetor body that includes the mounting flange and throttle body, the fuel bowl cover and fuel metering section and the air horn portions thereof, and that is adapted to be die cast from aluminum or other modern material.

Still another object of the invention is to die cast a single piece carburetor body by the use of three cores, in which case the cores can be made in sets so that carburetors of different capacity can be provided from the same die merely by substituting a different set of cores.

Another object of the invention is to provide a one piece die cast carburetor body having an integral fuel bowl cover, the bowl sealing surface of which is located above the normal fuel level in the bowl, and a metering section depending therefrom in a manner so that a separately formed fuel bowl may be secured to the carburetor, the result being that the metering section is suspended in and entirely surrounded by the fuel so as to be cooled thereby and does not at any point touch the fuel bowl wall.

Another object of the invention is to provide such a one piece updraft carburetor body having an integrally formed fuel inlet seat and float hinge pin trunnions, as well as universal choke and throttle shaft and lever mountings so that the carburetor may be mounted on either side of the engine.

Another object of the invention is to provide such a one piece updraft carburetor body having an integrally cast main nozzle.

A still further object of the invention is to provide such a carburetor body that may be formed by die casting aluminum, which inherently presents thick section porosity problems, in a manner to save metal and reduce subsequent machining operations, and at the same time reduce or eliminate porosity.

A further object of the invention is to provide a one piece die cast updraft carburetor body having an integral metering section that will on assembly of the carburetor be suspended near the center of the separate fuel bowl so as to reduce angularity problems, or related simulated angularity problems due to operation over rough terrain.

Another object of the invention is to provide a rugged tractor carburetor that is not only less expensive to manufacture due to the fact that many machining and assembly operations are eliminated, but is easier to clean and repair, this being due in part to an opening at the bottom of the carburetor body provided by one of the cores employed in casting the body.

Another object of the invention is to provide a carburetor body having an opening at the bottom of the bore thereof, said opening being adapted to be closed by a substantially flat member upon which engine pulsations may impinge at right angles so as to cause said pulsations to reverberate back to the engine and to trap pulsated fuel and prevent the same from entering the carburetor air intake.

These and other objects and advantages of the invention will become more apparent upon reference to the following specification and the attached drawings where- FIGURE 1 is a perspective view of a carburetor body embodying the invention so as to enable the same to be formed by die casting according to the invention, the dotted lines representing schematically the die block sections and cores that may be employed in die casting the body.

FIGURE 2 is a view similar to FIGURE 1, but taken from a direction opposite to that from which FIGURE 1 is taken.

FIGURE 3 is an enlarged cross-sectional view taken on the plane of line 33 of FIGURE 1, looking in the direction of the arrows, so as to illustrate the die block sections, the cores and the resulting cast carburetor body.

FIGURE 4 is a partial cross-sectional View taken on the plane of line 4-4 of FIGURE 3, looking in the direction of the arrows, to illustrate the configuration of the cores forming the venturi and the integral main nozzle.

FIGURE 5 is a partial cross-sectional view taken on the plane of line 55 of FIGURE 3, looking in the direction of the arrows, to further illustrate the coring for the venturi and the nozzle.

Referring now to FIGURES 1 and 2 in greater detail, the single piece updraft carburetor type body proposed to be die cast from any material amenable to die casting comprises an L-shaped structure, one leg of which comprises a horizontal air horn section 12 and the other leg of which comprises a vertical throttle body and venturi section 14, the free end of the section 14 terminating in the usual flange 16 by which the carburetor would be bolted to the engine intake manifold. It will be recognized that the terms horizontal and vertical are employed as a matter of convenience, since the carburetor would be mounted at the side of the tractor engine in substantially the position shown in FIGURE 1. In use of the completed carburetor, a hose connection would be made between an air cleaner and the free end of the air horn, the continuous bead 18 on the outer surface of the free end of the air horn being provided to improve the seal of the hose connection. When the carburetor is in operation, the air flows horizontally into the air horn and then upwardly through the venturi 20 (see FIGURE 3) and then into the engine intake manifold.

Suitable bosses 22 and 24 for mounting the choke and throttle shafts, respectively, are provided on both sides of the carburetor so that it may be mounted on either side of the engine. An internal vent for the carburetor fuel bowl is subsequently machined through the cast webs 26 and 28. A fuel bowl cover 30 is formed integral with the body 10, the cover extending generally in a direction opposite to that in which the air horn extends. The sealing surface 32 for the separate cast or stamped fuel bowl (not shown) lies in or adjacent and parallel to the plane of the venturi restriction. A metering section 34, which includes the usual main well, idle well, air bleed and accelerating pump capacities, is formed integrally with the fuel bowl cover, but it is spaced from the carburetor body in a manner so that the metering section will be suspended substantially into the center of the fuel bowl, which extends substantially half way around the portion 14, so as to be surrounded by the fuel therein. This provides cooling and angularity advantages in the carburetor. It will also be noted that the fuel inlet valve seat 36 and the float hinge pin trunnions 38 are also integrally cast.

Starting with the single piece body casting described above, only a minimum amount of simple machining and assembly operations are required to complete the carburetor.

As previously stated, the dotted lines of FIGURES 1 and 2 represent typical die sections fitted together to provide a mold to form the outer configuration of the carburetor body just described, the arrows indicating the directions in which the die sections would be pulled after casting to permit removal of the casting. The die sections making up the mold are labelled A, B and C, it being noted in FIGURE 1 that sections A and B are pulled apart to the left and right, respectively, and the section C, which extends over both sections A and B, is pulled downwardly.

Of course, in assembling the die sections for die casting a one piece body such as that described above, die sections A and B woud be moved inwardly and the die section C would be moved upwardly into engagement as shown in FIGURE 1, thereby forming a cavity conforming to the shape of the outer configuration of the desired casting. The die sections may be moved and secured in any manner known to the art.

As is apparent from FIGURE 3, the core D would then be moved upwardly through an opening 40 formed at the intersection of die sections A and B a controlled distance to form the underside of the venturi and the integral main nozzle. The core B would then be moved downwardly through an opening 42 formed at the intersection of the die sections A and B a controlled distance, at which time certain portions of the inner free end thereof would engage the inner free end of core D so as to form the upper side of the venturi and the upper portion of the nozzle 43. FIGURES 3, 4 and 5 illustrate one configuration of the inner free ends of cores D and E suitable for forming the venturi and the nozzle. Core E is also provided with pins 44 to form the holes 46 in the mounting flange 16 for receiving the mounting bolts.

After the cores D and E are assembled, the core F is moved inwardly through an opening 48 formed at the intersection of die sections A and B to form the air inlet passage 50, it being noted that the inner end of the core F has a concave configuration, as shown in FIGURE 3, to fit the cylindrical outer wall of core D.

Of course, all of the cores D, E and F are formed with a draft angle sufiicient to permit them to be pulled after molten metal has been forced under pressure, as is typical of the die casting process, to fill the cavity formed by the die sections and the cores and the casting has solidified. It will be noted further that the die section C has various projections extending therefrom to form the various passages in the metering section 34 of the carburetor body, as well as the space 52 between the metering section and the carburetor body section 14 required to receive the wall of the separate fuel bowl with sufficient clearance so that the metering section will be surrounded by fuel when the completed carburetor is in use.

The juncture of the fuel bowl cover 30 and integral metering section 34 with the carburetor body portion 14 results in a relatively thick section that would have an inherent tendency for porosity when the body is cast in aluminum. This tendency for porosity is reduced or eliminated by providing a pin 54 extending inwardly from die section B to form an internal vent cavity 56, part of which intersects the plane of the upper inner surface 58 of the fuel bowl cover 30 so that communication between the bowl and the cavity 56 is automatically provided when the cavity 56 is machined. Passages are subsequently drilled through the ribs 26 and 28 to communicate the cavity 56 with the air intake passage 50. Note also that the die blocks A and B are formed with an annular recess 60 for providing the head 18.

It is apparent from the above description that the invention provides a die casting method for forming a resulting single piece updraft carburetor body that meets the aforementioned objects and provides numerous advantages over prior updraft carburetor bodies and the prior art methods of forming the same.

For example, the resulting completed carburetor is less expensive and easier to manufacture, assemble and maintain. The carburetor and the configuration thereof is substantially leak proof, rugged and less subject to vapor metering and angularity problems, and it has been accepted in the agricultural tractor field where traditional practices constituted a natural barrier to change.

Due to the three-core method of die casting, the juncture between the air inlet and the bottom of the mixture passage, which may have nearly equal cross-sectional areas, provides a relatively large and unobstructed air reservoir, the bottom of which may be closed by a flat surface positioned at right angles to the direction of pulsations characteristic of recently developed tractor engines. The reservoir and the flat closure therefore provide means to reduce the severity of engine pulsations and to immediately recapture fuel that would otherwise be carried back to the air intake and cleaner system. This advantage of the invention is considered to be an important one that results directly from the proposed die casting method.

The invention has been described in such clear and concise terms as to enable anyone skilled in the art to practice the same. While a single embodiment has been shown and described for purposes of illustration, modifications may be possible, and no limitations are intended except as recited in the appended claims.

What I claim as my invention is:

1. A one piece body for an updraft type carburetor adapted to be formed by a three-core die casting method, said body as cast having a generally L-shaped configuration, one leg of said L having a passage extending all the way through said body, said passage having a venturi restriction, a mounting flange formed at the free end of said one leg, said passage having a positive draft angle from said venturi restriction to the opposite ends thereof, the other leg of said L having a passage intersecting said passage in said one leg of said L on the side of said venturi restriction opposite said mounting flange, said last named passage having a positive draft angle from the point of intersection to the free end of said other leg of said L, a fuel bowl cover extending from said body in a direction generally opposite to said other leg of said L, the fuel bowl engaging surface of said cover being positioned in the vicinity of said venturi restriction and normal to the axis of said passage having said venturi, and integrally formed fuel metering body extending from said cover in a direction parallel to the axis of said venturi but spaced from said body.

2. A one piece body for an updraft type carburetor and adapted to be formed by a three-core die casting method, said body as cast having a generally L-shaped configuration, one leg of said L having a passage extending all the way through said body, said passage having a venturi restriction, an integrally formed main nozzle extending from the wall of said passage adjacent said venturi, a mounting flange formed at the free end of said one leg, said passage having a draft angle from said venturi restriction to each end thereof, the other leg of said L having a passage intersecting said passage in said one leg of said L on the side of said venturi restriction opposite said mounting flange, said last named passage having a draft angle from the point of intersection to the end thereof, the outer free'end of said other leg of said L having a continuous bead formed on the periphery thereof, a fuel bowl cover extending from said body in a direction generally opposite to said other leg of said L, the fuel bowl engaging surface of said cover being positioned in the vicinity of said venturi restriction and normal to the axis of said passage having said venturi, and, an integrally formed fuel metering body extending from said cover in a direction parallel to the axis of said venturi but spaced from said body, the outer configuration of said body having positive draft angles from a plane passing through the centerlines of said passages.

3. A one piece body for an updraft type carburetor and adapted to be formed by a three-core die casting method, said body as cast having a generally L-shaped configuration, one leg of said L having a passage extending all the way through said body, said passage having a venturi restriction, an integrally formed main nozzle extending from the wall of said passage adjacent said venturi, a mounting flange formed at the free end of said one leg, said passage having a draft angle from said venturi restriction to each end thereof, the other leg of said L having a passage intersecting said passage in said one leg of said L on the side of said venturi restriction opposite said mounting flange, said last named passage having a draft angle from the point of intersection to the end thereof, a fuel bowl cover extending from said body in a direction generally opposite to said other leg of said L, the fuel bowl engaging surface of said cover being positioned in the vicinity of said venturi restriction and normal to the axis of said passage having said venturi, and an integrally formed fuel metering body extending from said cover in a direction parallel to the axis of said venturi but spaced from said body, the outer configuration of said body having positive draft angles from a plane passing through the centerlines of said passages.

4. A one piece body for an updraft type carburetor and adapted to be formed by a three-core die casting method, said body as cast having a generally L-shaped configuration, one leg of said L having a passage extending all the way through said body, said passage having a venturi restriction, an integrally formed main nozzle extending from the wall of said passage adjacent said venturi, a mounting flange formed at the free end of said one leg, said passage having a draft angle from said venturi restriction to each end thereof, the other leg of said L having a passage intersecting said passage in said one leg of said L on the side of said venturi restriction opposite said mounting flange, said last named passage having a draft angle from the point of intersection to the end thereof, the outer free end of said other leg of said L having a continuous bead formed on the periphery thereof, a fuel bowl cover extending from said body, the fuel bowl engaging surface of said cover being positioned in the vicinity of said venturi restriction and normal to the axis of said passage having said venturi, and an integrally formed fuel metering body extending from said cover in a direction parallel to the axis of said venturi but spaced from said body, the outer configuration of said body having positive draft angles from a plane passing through the centerlines of said passages.

References Cited UNITED STATES PATENTS 2,008,804 7/1935 Stokes 261-78 2,155,638 4/1939 Bracke 26172 3,207,490 9/1965 Sterner et a1. 261-72 X OTHER REFERENCES Die Casting: H. H. Doehler; McGraw-Hill Book Company Inc.; New York, N.Y., 1st ed., 1951, p. 184.

HARRY B. THORNTON, Primary Examiner.

RONALD R. WEAVER, Examiner. 

3. A ONE PIECES BODY FOR AN UPDRAFT TYPE CARBURETOR AND ADAPTED TO BE FORMED BY A THREE-CORE DIE CASTING METHOD, SAID BODY AS CAST HAVING A GENERALLY L-SHAPED CONFIGURATION, ONE LEG OF SAID L HAVING A PASSAGE EXTENDING ALL THE WAY THROUGH SAID BODY, SAID PASSAGE HAVING A VENTURI RESTRICTION, AN INTEGRALLY FORMED MAIN NOZZLE EXTENDING FROM THE WALL OF SAID PASSAGE ADJACENT SAID VENTURI, A MOUNTING FLANGE FORMED AT THE FREE END OF SAID ONE LEG SAID PASSAGE HAVING A DRAFT ANGLE FROM SAID VENTURI RESTRICTION TO EACH END THEREOF, THE OTHER LEG OF SAID L HAVING A PASSAGE INTERSECTING SAID PASSAGE IN SAID ONE LEG OF SAID L ON THE SIDE OF SAID VENTURI RESTRICTION OPPOSITE SAID MOUNTING FLANGE, SAID LAST NAMED PASSAGE HAVING A DRAFT ANGLE FROM THE POINT OF INTERSECTION TO THE END THEREOF, A FUEL BOWL COVER EXTENDING FROM SAID BODY IN A DIRECTION GENERALLY OPPOSITE TO SAID OTHER LEG OF SAID L, THE FUEL BOWL ENGAGING SURFACE OF SAID COVER BEING POSITIONED IN THE VICINITY OF SAID VENTURI RESTRICTION AND NORMAL TO THE AXIS OF SAID PASSAGE HAVING SAID VENTURI, AND AN INTEGRALLY FORMED FUEL METERING BODY EXTENDING FROM SAID COVER IN A DIRECTION PARALLEL TO THE AXIS OF SAID VENTURI BUT SPACED FROM SAID BODY, THE OUTER CONFIGURATION OF SAID BODY HAVING POSITIVE DRAFT ANGLES FROM A PLANE PASSING 